Hydraulically operated tamper

ABSTRACT

An impact tool driven by hydraulic fluid in which the motor piston is connected to the hammer by a light connecting rod. The hammer reciprocates in an air chamber which is isolated from the hydraulic fluid in the motor chamber by a split seal engaging the connecting rod. The connecting rod during reciprocation controls ports to supply fluid to alternate ends of the motor shuttle valve. A three position starting valve is operated manually by the trigger of the impact device to initiate movement of the shuttle valve into one extreme position in the event that the motor stops with the connecting rod in a position covering both shuttle valve control ports.

Lines Dec. 31, 1974 [73] Assignee: Praline industries lPty. Ltd.,

Elizabeth West, Australia [22] Filed: Nov. 10, 1972 [21] Appl. No.: 305,356

[30] Foreign Application Priority Data Nov. 15, 1971 Australia 7030/71 [56] References Cited UNITED STATES PATENTS 2,177,935 10/1939 Buck 173/127 X 3,339,644 4/1967 Klessig 173/127 3,399,602 9/1968 Klessig 173/168 X 3,605,916 9/1971 Voitsekhousky et a1. 173/139 3,695,366 10/1972 Klessig 173/134 Primary Examiner Ernest R. Purser Assistant Examiner-William F. Pate, lII Attorney, Agent, or FirmKinzer, Plyer, Dorn & McEachran [5 7] ABSTRACT An impact tool driven by hydraulic fluid in which the motor piston is connected to the hammer by a light connecting rod. The hammer reciprocates in an air chamber which is isolated from the hydraulic fluid in the motor chamber by a split seal engaging the connecting rod. The connecting rod during reciprocation controls ports to supply fluid to alternate ends of the motor shuttle valve. A three position starting valve is operated manually by the trigger of the impact device to initiate movement of the shuttle valve into one extreme position in the event that the motor stops with the connecting rod in a position covering both shuttle valve control ports.

2 Claims, 2 Drawing Figures mama Dec. 3 1974 2 Quota-Shoot 1 Patented Dec. 31 1974 3,857,448

5% Sheets-Sheet 2 v Nv C n Ms Mm aw I lill i i 1. I I|\ HYDRAULICALLY OPERATED TAMPER This invention relates to a hydraulically operated tamper.

BACKGROUND OF INVENTION It is already known to operate tampers hydraulically, this type usually comprising a cylinder in which a piston operates, the piston actuating the tamper mechanism itself which extends from the piston outwardly from the cylinder to terminate in a tamper which may be interchangeable by having the tamper engage a socket in the piston assembly.

It is common in such tampers to use the piston rod itself as a valve spool to control the flow of hydraulic fluid to a control valve which regulates the flow to the piston to give the power stroke and the return stroke.

In units of this type there is a problem in starting the actuation of the piston from some positions, but in the devices as used heretofore the starting problem could be overcome by moving the tamper itself to position the piston, and thus the control valve regulated by it, to a part of the cycle where the pressure oil then takes over and continues to operate the piston in its tamping cycle.

Certain problems occur however with the prior art devices, such as are caused by the mass of the moving parts, which reduces efficiency, and the method of imparting the blow of the piston to the tamper.

Also it is generally necessary to have relatively large oil flow to achieve the required tamping pressures and velocities, and generally it is desirable to provide certain improvements'to tampers of the type known at present which it is the object of this invention to achieve.

Thus one of the objects of the present invention is to so arrange the hydraulic piston and its mounting that it can be of minimum size to thus reduce mass and give faster and more efficient operation.

A further object of the invention is to reduce the resistance to movement of the hammer itself which strikes the tamping tool holder so that while the hammer can have a required mass, it is not damped by the presence of hydraulic fluid by means of which the device is operated.

A still further object is to provide ready starting of the mechanism without having to move the piston by means of the tamper itself.

A further object of the invention is to give better hammer control through the valve mechanism such that hydraulic fluid which operates the piston has its cycle so controlled that when bleed is cut off and full hydraulic pressure is applied to the piston, the hammer will already be on its way in the other direction.

This and other objects of the invention will be appreciated from the following description.

SUMMARY OF INVENTION The device according to the present invention comprises a housing in which operates a small elongated piston which also acts as the control for moving a control valve which regulates the flow of hydraulic fluid to the piston, the control valve itself being supplied with pressure fluid when a trigger is actuated which opens a starting valve and which ensures starting and then allows continued movement of the unit when the starting valve is moved to a running position, the hydraulically operated piston extending through a split gland to allow the piston rod to be of the smallest possible diameter, the hammer being mounted on the piston rod but in a chamber remote from the oil circuit so that the hammer operates in an independent air space, the hammer in the air chamber in turn being adapted to strike an anvil and tool holder into which the tamping tool can be clipped to allow different tamping tools to be engaged in this holder.

Thus the invention essentially comprises a hydraulically operated piston of small dimensions with a light actuating rod between it and a hammer in an air chamber, the piston being isolated from the air chamber by a split seal engaging a relatively small diameter connecting portion between the operating piston and the hammer so that the mass of the piston is reduced, while the hammer weight can be increased for the same total assembly weight. Because the hammer is situated in an air chamber, it can be moved in a much more effective manner without damping which would occur if the hammer were disposed in the hydraulic fluid chamber.

By use of a starting valve which moves a control valve to a position where it regulates movement of the piston, the device will continue to function when once started and no pressure need be applied to the tamping tool to move the piston into a starting position as was usually necessary heretofore.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side elevation of the invention FIG. 2 is an enlarged longitudinal central sectional view of the invention DESCRIPTION OF PREFERRED EMBODIMENT An elongated housing 1 is provided at its one end with a hand grip 2 whereby the tamping tool can be manipulated and has at its other end a tool holder 3 which is axially slidable within a bearing member 4 but is confined in its axial movement by a movable retractable jaw 5 so that it remains in contact with an anvil 6 disposed in the path ofa hammer 7 by means of which the blows are imparted, the anvil and hammer being axially movable in a guide member 8 the forward part of which forms a cylindrical guide 9 for the hammer 7. The cylindrical guide member is surrounded by a sleeve 10, and the cylindrical guide 9 has ports 11 at each end to isolate air displaced by the hammer 7 as it reciprocates, so that the hammer operates in clean air.

From the foregoing it will be realised that the hammer, though coupled to the piston which operates it, is disposed in a separate chamber formed by the cylindrical guide 9 and operates in a sealed air chamber 9 into which the anvil 6 projects from one end, and the rod of the piston 15 from the other end.

The hammer 7 has a semispherical socket 16 in it which engages a semispherical end 17 on the piston rod 18, the end 17 being confined in the socket 16 by a nut 19 which presses against a split washer 20 which has a resilient washer 21 between it and the inner part of the semispherical end on the piston to hold the hammer 7 to the piston but permit it to accomodate itsef to the cylindrical guide 9.

The tool can extend the required distance from the bearing member 4, and will be provided with tamping means or cutting means on its remote end according to requirements.

The piston is of relatively small diameter and is positioned at one end of the piston rod 18 which is of a lesser diameter than the piston 15 to reduce weight of the assembly and also give a stepped piston, this rod extending through a split gland which is held in place by a nut 26 and which isolates the hydraulic fluid which actuates the piston 15 from the air chamber 9 on the other side of the gland 25 in which the hammer 7 operates, the split gland being preferably formed of a special material such as filled Teflon which can build up the space between the reduced diameter of the piston rod 18 and the larger diameter of the piston, 15 the piston 15 thus being insertable into the cylinder 24 through the opening in which the gland is positioned, but the gland then filling this space to provide the seal. To form the gland, a tubular piece of filled Teflon is split so that it can be engaged around the reduced diameter rod, and it will then close on the rod to form an effective seal between the part of the cylinder 24 which contains hydraulic fluid, and the air chamber 9 on the other side of the gland 25, this smaller effective piston area on one side of the gland thus being isolated from the air space 9 in which the hammer operates.

An O-ring can be incorporated in the split gland to reduce leakage if this is desired but is not shown.

The piston 15 has a groove 27, and this, and the reduced diameter of the piston rod 18, act to control the operation of the control valve 28 which regulates the operation of the piston 15, the two ends of the control valve 28 being connected to the ports 29 and 30 in the wall 31 of the cylinder 24 in which the piston 15 operates.

The control valve 28 is movable in a bore 32 in a valve housing 33 and is arranged to either place the port 34 which communicates with the bore of the cylinder 24 into communication with the valve port 35 or the valve port 36, one port 35 being a pressure port and the other port 36 an exhaust port.

Fluid is fed to a pressure chamber 40 surrounding the cylinder 24 by the manual control valve 41, and has access to the bore of the cylinder 24 through the two ports 43 and 44, the port 43 allowing return pressure to be applied to the rear wall of the piston 15 at all times, the piston being advanced against this pressure when the control valve 28 allows pressure fluid to flow through the port 34 to the larger effective area end of the piston 15.

Reciprocation of the piston is thus caused by a pressure differential on its two ends, the one end having its area restricted due to the piston rod 18 which extends from it, and as said, the rear wall of the piston has a constant pressure supply for piston return, the piston being moved forward by the application of pressure to its full area face 46.

At the same time, the control valve 28 is actuated as the ports 29 and 30 are uncovered by the piston 15, the operation being as follows:

When the piston 15 reaches the end of its driving stroke, that is its end 45 approaches the port 43, the duct 29 is placed into communication with the port 44 through the groove 27 in the piston 15 and the shuttle valve 28 is then moved to the opposite end to that shown in FIG. 2. This now cuts off the mains port 35 and opens the exhaust port 36 to the end 46 of the piston 15.

Differential pressure on the end 45 of the piston now moves the piston on its return stroke carrying the hammer 7 with it.

When the end 45 of the piston passes the port 30, pressure is applied to the lower end of the shuttle valve 28, but as the port 29 is covered by the piston 15, the valve 28 moves across for the next pressure stroke as bleed takes place through the duct 47, which leads to the exhaust port 36, and as the shuttle valve 28 moves to the position shown in FIG. 2 the pressure is applied to that end 46 of the piston and it is brought to rest and reversed in its stroke to give the next power stroke to the piston 15 and hammer 7.

In its power stroke the piston closes the port 30, but the shuttle valve 28 remains in its upper position as shown in FIG. 2 until the port 29 is again uncovered by the groove 27 and the shuttle valve is driven down to cut off the mains pressure from the piston end 46 and institute communication with the exhaust, the port 30 having a small bleed duct 48 leading to the exhaust port 36.

The size of the ducts 47 and 48 control the speed of movement of the control valve 28.

The control valve 28 which controls the hydraulic function of the piston 24 is disposed at right angles to the axis of this piston.

The manual starting valve 41 is parallel to the main piston-controlling control valve 28, but this is actuated by a trigger 50 on the hand grip 2.

The reason why a starting valve is required is that in for instance a central position where the piston covers both ports 29 and 30, the control valve 28 could not be moved by pressure fluid, and as the hammer 7 is not coupled to the anvil 6, no pressure to move it manually could be applied. For this reason a three position starting valve is used, the first position cutting off the pressure fluid, the second position being a starting position where the control valve 28 is moved to one extreme to move the piston 15 correspondingly and the final position being the operating position where the unit is under control of the control valve 28 as the manually controlled starting valve is now cut off and cannot hold the control valve in one extreme position.

In FIG. 2 the valve 41 is shown in the of position and the duct 51 in the starting valve does not register with the duct 52 which opens at to the chamber of the control valve. The main pressure supply enters at 54 and is cut off from the groove 55. When the valve 41 is moved inwards against the spring 56 by the control lever 57, the duct 51 opens to the duct 52 and the groove 55 opens to the pressure inlet 54 and pressure is applied to the control valve 28 through the duct 52 to move it to its pressure position (as in FIG. 2) and pressure fluid flows to the duct 34 and end 46 of the piston. This positions the control valve 28 and piston 15 for starting, but action does not commence because the valve is still held until the manual starting valve 41 is moved further to bring the ducts 51 and 52 out of register and fully open the groove 55 to the main inlet 54. The groove 55 opens both to the valve port 35 and the chamber 40 through ducts 59.

From the foregoing it will be realised that the control valve 41 causes a flow of pressure fluid to take place to the piston 15 through the main control valve 28 which will move the piston to one end of its stroke, after which the central valve 28 is held in its operating position and flow of hydraulic fluid will take place through it to the shuttle valve and to the chamber 40, and in this position operation will continue under control of the control valve 28.

Thus a simple and effective device is provided in which the piston, which is pressure fluid operated, can be of relatively small size and this piston in turn has a connecting rod 18 which projects into an air chamber 9 in which the hammer 7 is situated, the hammer 7 being positively but flexibly coupled to the piston 15 through the piston rod 18 so that it moves with the piston, but in an air space 9 from the hydraulic part of the system, whereby the hammer 7 can be of relatively substantial size to store energy from the operation of the piston 15 and thus give a required blow to the anvil 6 which also projects into the air 9 in which the hammer 7 operates. The piston 15 and piston rod 18 and ball end 17 are preferably made in one piece to reduce mass, the difference in diameter between the piston 15 and piston rod 18 giving an assisting differential action so far as the hydraulic pressures are concerned.

Because the hammer 7 is in an air space 9, cushioning of the hammer 7 could take place at the two ends of its motion by appropriately arranging the air space 9 and bleeds ill thereto.

Because the hydraulic piston 15 is isolated from the hammer, 7 a small piston can be used which need only have a relatively small diameter rod 18 connecting it to the hammer, the main dynamic mass of the unit itself being the hammer 7 so that the most effective use is made of the hammer when striking the anvil 6 of the tool holder, to thereby impart highly effective action to the tamping tool, the hammer itself thus being controllable for high speed operation because the concentration of the mass is at the required locality.

The retractable jaw 5 can be of U-shape with its arms 60 engaged by pivots 61 on blocks 62 which engage bolts 63 held by loading springs 64 so that the blocks 62 hold square ends of the arms 60 against the bearing member 4 but allow the jaw 5 and arms to be swung out of the way of the tool holder 3 by pulling the blocks 62 and bolts 63 outwards against the action of the spring 64. Rotation of the tool holder 3 is prevented by having a hexagon section 65.

Return travel of the hammer 7 is limited by a resilient ring 70 and by air compression as the hammer passes the port 11, while seals 71 are used where necessary to limit outflow of hydraulic fluid from the system. A resilient washer 72 reduces noise by cushioning the return of the tool and anvil.

I claim:

1. In a fluid operated tamper comprising a housing providing a cylinder bore in which a piston rod supporting a hammer head is disposed for reciprocation during forward and return strokes: a pressure chamber in the housing for receiving operating fluid under pressure to be communicated to said cylinder bore through supply port means located along the axis of the cylinder bore, said piston rod presenting a piston of predetermined large area and a rear wall of smaller area, first and second ducts within said housing communicating with the bore of the cylinder and each duct opening respectively into opposite ends of a valve chamber which has a fluid operated shuttle valve therein, said valve being cycled by alternately pressurizing and exhausting the opposite ends of said valve chamber, valve means on said piston rod whereby said ducts in the cylinder bore are alternately covered and uncovered with respect to said supply port means during reciprocation of the piston rod thereby to furnish operating fluid alternately to said ducts for pressurizing alternate ends of said valve chamber to operate the shuttle valve, pressure and exhaust ports in said valve chamber for translating fluid to and from the piston and the piston rod rear wall, said shuttle valve in one position communicating said pressure port to the head of the piston while concurrently communicating the exhaust port to said rear wall and vice versa in a second position of the shuttle valve thereby to reciprocate the piston rod in forward and return strokes, and a starting valve means to start reciprocation of the piston rod when the valving means on the piston rod close both of said ducts, said starting valve means comprising a three position manually operated valve operating in a valve bore and affording:

a. a main port for fluid under pressure to operate said tamper, being closed by the starting valve in a first position, and passage means for connecting said main port to the pressure chamber in the housing and to one of the ends of the shuttle valve chamber and to the pressure port of the shuttle valve;

b. said starting valve having a second position where said main port is so connected to said passage means thereby to furnish operating fluid under pressure to said pressure chamber, to one end of said shuttle valve chamber and to the pressure port of the shuttle valve; and

c. said starting valve having a third position where communication is disestablished between said main port and said one end of the shuttle valve chamber while maintaining communication between said main port and the passages leading therefrom to said supply chamber and the pressure port of the shuttle valve.

2. In a fluid operated tamper comprising a housing providing a cylinder bore in which a piston rod supporting a hammer head is disposed for reciprocation during forward and return strokes: a pressure chamber in the housing for receiving operating fluid under pressure to be communicated to said cylinder bore through first and second spaced supply ports along the axis of the cylinder bore, said piston rod presenting a piston of predetermined large area and a rear wall of smaller area, first and second ducts within said housing communicating with the bore of the cylinder and each duct opening respectively into opposite ends of a valve chamber which has a fluid operated shuttle valve therein, said valve being cycled by alternately pressurizing and exhausting the opposite ends of said valve chamber, valve means on said piston rod whereby said ducts in the cylinder bore are alternately covered and uncovered with respect to said ports during reciprocation of the piston rod thereby to furnish operating fluid alternately to said ducts for pressurizing alternate ends of said valve chamber to operate the shuttle valve, pressure and exhaust ports in said valve chamber for translating fluid to and from the piston and the piston rod rear wall, said shuttle valve in one position communicating said pressure port to the head of the piston while concurrently communicating the exhaust port to said rear wall and vice versa in a second position of the shuttle valve thereby to reciprocate the piston rod in forward and return strokes, and a starting valve means to start reciprocation of the piston rod when the valving means on the piston rod close both of said ducts, said starting valve means comprising a three position manually operated valve operating in a valve bore and affording:

a. a main port for fluid under pressure to operate said tamper, being closed by the starting valve in a first position, and passage means for connecting said main port to the pressure chamber in the housing and to one of the ends of the shuttle valve chamber and to the pressure port of the shuttle valve;

b. said starting valve having a second position where said main port is so connected to said passage means thereby to furnish operating fluid under pressure to said pressure chamber, to one end of said shuttle valve chamber and to the pressure port of the shuttle valve; and

. said starting valve having a third position where shuttle valve. 

1. In a fluid operated tamper comprising a housing providing a cylinder bore in which a piston rod supporting a hammer head is disposed for reciprocation during forward and return strokes: a pressure chamber in the housing for receiving operating fluid under pressure to be communicated to said cylinder bore through supply port means located along the axis of the cylinder bore, said piston rod presenting a piston of predetermined large area and a rear wall of smaller area, first and second ducts within said housing communicating with the bore of the cylinder and each duct opening respectively into opposite ends of a valve chamber which has a fluid operated shuttle valve therein, said valve being cycled by alternately pressurizing and exhausting the opposite ends of said valve chamber, valve means on said piston rod whereby said ducts in the cylinder bore are alternately covered and uncovered with respect to said supply port means during reciprocation of the piston rod thereby to furnish operating fluid alternately to said ducts for pressurizing alternate ends of said valve chamber to operate the shuttle valve, pressure and exhaust ports in said valve chamber for translating fluid to and from the piston and the piston rod rear wall, said shuttle valve in one position communicating said pressure port to the head of the piston while concurrently communicating the exhaust port to said rear wall and vice versa in a second position of the shuttle valve thereby to reciprocate the piston rod in forward and return strokes, and a starting valve means to start reciprocation of the piston rod when the valving means on the piston rod close both of said ducts, said starting valve means comprising a three position manually operated valve operating in a valve bore and affording: a. a main port for fluid under pressure to operate said tamper, being closed by the starting valve in a first position, and passage means for connecting said main port to the pressure chamber in the housing and to one of the ends of the shuttle valve chamber and to the pressure port of the shuttle valve; b. said starting valve having a second position where said main port is so connected to said passage means thereby to furnish operating fluid under pressure to said pressure chamber, to one end of said shuttle valve chamber and to the pressure port of the shuttle valve; and c. said starting valve having a third position where communication is disestablished between said main port and said one end of the shuttle valve chamber while maintaining communication between said main port and the passages leading therefrom to said supply chamber and the pressure port of the shuttle valve.
 2. In a fluid operated tamper comprising a housing providing a cylinder bore in which a piston rod supporting a hammer head is disposed for reciprocation during forward and return strokes: a pressure chamber in the housing for receiving operating fluid under pressure to be communIcated to said cylinder bore through first and second spaced supply ports along the axis of the cylinder bore, said piston rod presenting a piston of predetermined large area and a rear wall of smaller area, first and second ducts within said housing communicating with the bore of the cylinder and each duct opening respectively into opposite ends of a valve chamber which has a fluid operated shuttle valve therein, said valve being cycled by alternately pressurizing and exhausting the opposite ends of said valve chamber, valve means on said piston rod whereby said ducts in the cylinder bore are alternately covered and uncovered with respect to said ports during reciprocation of the piston rod thereby to furnish operating fluid alternately to said ducts for pressurizing alternate ends of said valve chamber to operate the shuttle valve, pressure and exhaust ports in said valve chamber for translating fluid to and from the piston and the piston rod rear wall, said shuttle valve in one position communicating said pressure port to the head of the piston while concurrently communicating the exhaust port to said rear wall and vice versa in a second position of the shuttle valve thereby to reciprocate the piston rod in forward and return strokes, and a starting valve means to start reciprocation of the piston rod when the valving means on the piston rod close both of said ducts, said starting valve means comprising a three position manually operated valve operating in a valve bore and affording: a. a main port for fluid under pressure to operate said tamper, being closed by the starting valve in a first position, and passage means for connecting said main port to the pressure chamber in the housing and to one of the ends of the shuttle valve chamber and to the pressure port of the shuttle valve; b. said starting valve having a second position where said main port is so connected to said passage means thereby to furnish operating fluid under pressure to said pressure chamber, to one end of said shuttle valve chamber and to the pressure port of the shuttle valve; and c. said starting valve having a third position where communication is disestablished between said main port and said one end of the shuttle valve chamber while maintaining communication between said main port and the passages leading therefrom to said supply chamber and the pressure port of the shuttle valve. 